Dual focus objective lens with two curvatures for focussing light on two different kinds of disks with different thicknesses

Abstract

A dual-focus objective lens for an optical pickup which is compatible with both 0.6 mm and 1.2 mm disks is compensated in its aberration with respect to a light spot on a recording plane of the loaded disk and at least one of a light-receiving plane and a light-emitting plane of the dual focus objective lens has a first curvature unit and a second curvature unit whose curvature radii are different from each other. Incident light beams passing through the whole region of the first curvature unit and second curvature unit are focused onto the thinner disk, and parts of incident light beams passing through the region around the first curvature unit are focused onto the thicker disk. In the optical pickup having the dual focus objective lens, since the light is not divided, light efficiency is improved, thereby reproducing a signal with a high signal-to-noise ratio. Particularly, an optical pickup enabling recording as well as reproduction is obtained.

Dependencies are inferred from the claim text.